The invention relates to a method of recording a digital information signal in information tracks of a record carrier, which method comprises the conversion of consecutive information words of the applied digital information signal into channel words of a selected channel code prior to recording, which channel code has been selected so that for each information word of the applied digital information signal, a first and a second channel word are available, the first channel word forming part of a group of permissible channel words with a d.c. content unequal to zero and the second channel word being the complement of the first channel word.
The invention also relates to a recording apparatus for carrying out the method, a record carrier provided with a digital signal obtained by means of this method, and a read apparatus for such a record carrier.
Such a method is known, for example, from an article in NTZ, 1970, Heft 1, pp. 11-16, entitled "Zusammenstellung und Gruppierung verschiedener Codes fur die Uebertragung digitaler Signale". In the case of the so-called Bimode-Code described in this article on page 12 under 2.3.b., each information word of the information signal yields two channel words with identical but opposite d.c. content for the conversion of the applied digital signal into the channel code. The choice between the two available channel words is then made depending on the d.c. content of the preceding channel words, steps being taken to minimize the d.c. content of the digital signal to be recorded.
This code may be applied to binary signals for which each data bit of a channel word can assume only two possible values. Moreover, this code may also be applied to multivalent signals, i.e. signals for which each data bit of a channel word can assume more than two possible values, for example a ternary signal. A Bimode-code for such a ternary signal is also described in said article on page 15.